The present invention relates to manholes in large container vehicles for dry bulk products. In particular, the present invention relates to locking levers and sealing gaskets for securing the cover on such manholes.
Container vehicles such as railcars and truck trailers used for transporting dry bulk products such as grains or powdered cement typically have manhole access ports on their top sides which allow workers to climb into the container vehicle and inspect or clean the interior of the container. Normally to unload a container vehicle, pressurized air is applied to the interior of the container and the products are carried by the escaping air through an outlet located near the bottom of the container. Naturally, the manholes must be sealed while the container vehicle is being unloaded to prevent air from exiting the manhole cover rather than the intended container outlet. Also, when transporting cargo, it is desirable to maintain an air tight seal in order to prevent contamination of the cargo by outside elements and moisture. A typical system for covering and sealing the manhole is seen in FIGS. 1-3. FIG. 1 illustrates a typical dry bulk container vehicle 100. FIG. 1 shows how container vehicle 100 will have one or more manholes 1. FIG. 2A illustrates prior art manhole 1 in greater detail. A cylindrical weld ring 3 will surround the opening in the container vehicle and be welded to the body of the vehicle. A cover 2 will be attached to weld ring 3 by way of hinge 4 as best seen in the side view of FIG. 2B. It can be seen in FIG. 2B that a gasket 6 is positioned around an underside perimeter of cover 2 and will rest on the upper edge of weld ring 3. It will be understood that gasket 6 forms a seal between the upper edge of weld ring 3 and cover 2. FIG. 3 shows how gasket 6 will be position in a gasket channel 7 with inwardly sloping sidewalls 8.
FIG. 2A illustrates how a series of cam lever assemblies 10 will be positioned around the outside perimeter of cover 2. Each cam lever assembly 10 will have a cam handle 11 and a forked end 17 opposite handle 11. Each prong of forked end 17 will have a pin aperture 22 formed therein and will also include a cam surface 18 formed on the lower portion of the prong. As best seen in the cross-section view of FIG. 3, an adjusting screw 12 is pinned between the prongs by a pivot pin 13. Adjusting screw 12 extends through cover 2 and engages jam nut 14 and connector 15. It will be understood that jam nut 14 acts as a locking mechanism and will not allow downward travel of screw 12 when jam nut 14 is positioned against connector 15. FIG. 2A illustrates how connector 15 will be connected to weld plate 3 by way of brackets 25 and clevis pin 20. Returning to FIG. 3, it can be visualized how the rotation of adjusting screw 16 will raise or lower cam surface 18 and cause cam surface 18 to place either more or less pressure on cover 2. Typically, a wear plate 19 is positioned on cover 2 and provides the actual surface which cam surface 18 engages. Wear plate 19 may be constructed of a wear resistant and rust resistant material such as stainless steel and operates to prevent the frictional force of cam surface 18 from damaging cover 2. Wear plate 19 may be screwed to cover 2 (see FIG. 2A) in order that it may be easily replaced when it becomes excessively worn.
FIG. 2A best illustrates how locking lever assembly 10 operates to hold cover 2 tightly closed against weld ring 3. One lever handle 11A is shown rotated back and completely removed from engagement with cover 2. When it is desired to place pressure on cover 2, the cam lever handle is placed in the upper position as shown by lever handle 11C. At this point, cam surface 18 has not engaged wear plate 19 and forced cover 2 downward. As cam handle 11C is rotated forward, cam surface 18 begins to engage wear plate 19 and exert a downward force on cover 2. When cam lever handle 11C is rotated fully forward as shown by cam lever handle 11B, a flat portion of cam surface 18 rests upon wear plate 19 and tends to resist upward rotation of cam lever handle 11. Over time, wear plate 19 and gasket 6 may become worn. To maintain a proper seal between weld ring 3 and gasket 6, it will be necessary to press cover 2 further downward or in other words, bring cam surface 18 closer to connector 15. This may be accomplished by positioning the cam lever handles as seen for handle 11C. Handle 11C may then be rotated which will cause adjusting screw 12 to travel further down the threaded surface of connector 15. This results in cam surfaces 18 being moved correspondingly closer to connector 15. Therefore, when handle 11C is rotated forward in the closed position, cam surface 18 will apply a greater downward force to wear plate 19 and thus press gasket 6 more firmly onto weld ring 3.
FIG. 2A also shows safety catch 23. Safety catch 23 rotates over wear plate 19 as suggested by viewing the safety catch 25 shown on handles 11A and 11B. The purpose of safety catch 23 is to prevent cover 2 from being xe2x80x9cblownxe2x80x9d open if the container is pressurized when all cam handles 11 are released. If air pressure is pushing cover 2 upward, safety catch 23 is engaged by wear plate 19 and cannot be rotated backwards. It is necessary for pressure to bleed off and cover 2 to rest on weld ring 3 before safety catch 23 may rotate backwards. Normally, only one cam lever assembly 10 will have a safety catch 23. FIG. 2A illustrates two safety catches 23 in order to show one in the rotated backwards (open) position and one in the rotated forward (closed) position. There are several disadvantages to the prior art cam lever assembly 10. First, adjusting screw 12 may only be rotated when handle 11 is not in the forward or locked position. Thus, to adjust screw 12, handle 11 must be lifted and the downward force on wear plate 19 released. If cover 2 is forming a pressure seal with weld ring 3, releasing force on wear plate 19 may undesirably allow gases within the container vehicle to escape. Second, when handle 11 is rotated, it must be rotated in complete revolutions in order for handle 11 to be able to rotate forward to the locked position. Thus, if the desired adjustment is xc2xd a turn of adjustment screw 12 or 1xc2xd turns, this cannot be achieved. Adjustment screw 12 must be turned in increments of 360 degrees, even if this causes cam surface 18 to place more or less force on wear plate 19 than is desired. Placing to little force prevents the formation of an effective pressure seal. On the other hand, placing too much tends to damage and shorten the life of gasket 6.
Other problems also arise with the prior art gasket 6. As gaskets become old, they tend to stick to the rim of weld ring 3 and are too easily pulled out of gasket channel 7. Attempts have been made to fix gasket 6 in channel 7 with an adhesive, but this creates its own set of problems. For example, adhesives which are not evenly applied may form lumps under gasket 6, lessening the gasket""s ability to seal uniformly. Moreover, when it becomes necessary to replace gasket 6, gasket 6 may tear and leave segments of the gasket still glued within channel 7. This necessitates the time consuming task of clearing out all the small bits of the old gasket remaining in channel 7 before the new gasket may be inserted. It would be a significant advance in the art to provide a cam lever assembly and gasket which overcomes the above described disadvantages.
The present invention provides a sealable manhole system having a weld ring, a cover with a gasket shaped to engage said weld ring, and a cam lever assembly. The cam lever assembly comprising includes a cam lever having a cam surface and a pivot aperture. A pivot pin is sized to engage the pivot aperture and has a screw aperture formed there through. A connector operatively attached to the weld ring and an adjustment screw passes through the screw aperture and engages the connector.
The invention further includes a sealable manhole system having a weld ring and a cover with a gasket shaped to engage the weld ring, and a cam lever assembly. The cover further includes a gasket channel with a neck and an internal shoulder formed above the neck. The internal shoulder further has a dimension wider than the neck and is oriented at an angle to the neck.